Muffling device



Patented Aug. 30, 1938 UNITED STATES MUFFLING DEVICE George H. Fuehrer, Phillipsburg, N. J., assigncr to Ingersoll-Rand Company, Jersey City, N. J., a corporation of New Jersey Application April 9, 1937, Serial No. 135,831

4 Claims.

This invention relates to muffling devices, and more particularly to a mufiiing device adapted to receive the exhaust fluid from a. pneumatic tool of the percussive type.

One object of the invention is to suppress the noise induced by the exhaust fluid issuing from the pneumatic tool.

Another object is to effectively shield the pneumatic tool against the chilling effects of the expanded fluid flowing through the muiiiing device, and still another object is to equip the pneumatic tool with a simplified and efiective mmiling device of light weight and which may be readily and cheaply replaced.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawing accompanying this specification and in which similar reference numerals refer to similar parts,

Figure 1 is an elevation, in section, of a mufiiing device constructed in accordance with the practice of the invention and showing it applied to a pneumatic tool of the percussive type, the tool being partly broken away, and

Figures 2 and 3 are transverse views taken through Figure 1 on the lines 2-2 and 3-3, respectively.

Referring more particularly to the drawing, the muflling device, designated in general by 2D, is shown applied to a fluid actuated percussive tool it comprising a cylinder 22 and front and back heads 23 and 24, respectively.

The interior of the cylinder constitutes a piston chamber 25 containing a hammer piston 26 which actuates a working implement 21 extending into the front head and controls the free exhaust port 23 for the piston chamber 25. The piston is of the differential type and has a stem 29 which extends slidably through a bushing 30 in the front end of the piston chamber to strike against the working implement 21.

The pressure fluid employed for actuating the piston 26 may be distributed to the ends of the piston chamber 25 by suitable valve mechanism of which only the outer casing part 3| is shown. The valve mechanism may, as illustrated, be arranged between the piston chamber and the back head 24 and be in communication with the ends of the piston chamber through the usual ports and passages (not shown).

The muffier constructed in accordance with the practice of the invention, is in the form of a tubular member or sleeve 32 which surrounds the intermediate portion of the pneumatic tool or, more particularly the valve mechanism 3i and that portion of the cylinder defining the piston chamber 25. The rearriost end 33 of the sleeve 32 seats against a shoulder at of the back head it and is centralized with respect to the back head by a projection of the back head extending into the sleeve. Thefront end 36 of the sleeve encircles the boss 31 on the front head and abuts a shoulder s52, also on the front head.

The sleeve is of larger diameter than the cylinder and cooperates therewith to define an expansion space or chamber is to receive the exhaust fluid issuing from the port 263. At the ends of he expansion chamber are transverse ring plates M5 and it which may be suitably secured to the inner surface of the sleeve 32. The plate Ml, which forms the upper bounding surface of the chamber is disposed intermediate the exhaust port 23 and the valve mecha nism 32 to protect the valve mechanism against exposure to the expanded fluid flowing through the chamber The plate 40 serves a similar function with respect to the parts lying immediately forwardly of the front end of the piston chamber 25.

In order that maximum suppression of the sound waves be obtained in the expansion chamber 3b a. series of baflles 52, Q3, and d5 are arranged therein in staggered relationship with respect to each other and to extend longitudinally of the chamber 3? The may be said to be arranged in groups on opposite sides of the exhaust port Those designated 42 and 33 constitute one group of which the baffie t2 extends from the uppermost portion of the chamber St to a point near the partition M, thus leaving a space it between the baffle and the partition through which fluid may flow into the space between the battles 42 and 43. The bafile 43, on the other hand, abuts the partition 4| and terminates a suflicient distance below the partition 43 to provide a space M between the baflle 13 and the partition 4 for the free passage of fluid into the portion of the chamber 39 wherein final expansion of the exhaust fluid takes place before it passes to the atmosphere through outlet openings ts in the sleeve and preferably located adjacent the partition M.

The other group of battles, consisting of those designated 4 3 and t5, are arranged in substan tially the same manner as the baffles 42 and 43, respectively. More specifically, the arrangement of the baflie 44 corresponds with that of the baffle Q2 and the baffie 2-5 is arranged in the manner of the bafile Q3. Thus, as will be readily ill) understood, two tortuous paths are provided for the passage oi the exhaust fluid from the exhaust port 28 to the outlet openings G8. The fluid is thereby required to travel along extended paths and a maximum damping effect is, therefore, obtained.

To the end that the portion of the cylinder lying in the transverse plane of the expansion chamber 39 may be amply protected against exposure to the low temperature resulting upon expansion of the fluid issuing from the exhaust port 28, the cylinder is encased in a jacket 49 of insulating material, as for example fibre. The jacket 49 may fit the cylinder 22 snugly. Its upper and lower ends are preferably embedded in the back head 24 and the partition 4 I, respectively. In the periphery of the jacket 49 are 1ongitudinally extending grooves 50 which interlockingly engage the inner edges of the bailles to assure against relative rotation between the sleeve 32 and the jacket 49 and also to maintain the jacket seated against the cylinder.

In order to prevent buckling or distortion of the jacket 49 as a result of expansive and contractile movements of the metal parts incident to their exposure to temperatures of widely spaced degree, a rubber ring 5| is disposed in the partition M to act as a seat for the adjacent end of the jacket. The ring 5| may be of such thickness as to cause partial displacement of the rubber when the casing parts of the rock drill and the muifiing device are clamped together, in assembled relationship. The jacket 49 will thereby, at all times, be held against endwise vibratory movement and consequent damage.

As is well known under certain climatic conditions the temperature resulting upon expansion of the exhaust fluid causes the moisture en-- trained by the fluid to congeal and seriously restrict the areas of the passages through which the fluid flows to the atmosphere. In order to prevent an occurrence of this nature in the immediate vicinity of the exhaust port 28 a flexible sheet or flap 52 of rubber or fabric is arranged within the sleeve to confront the exhaust port 28.

To the end that an undulatory or flapping motion of the sheet 52 may be effected said sheet is suspended from the partition 40 and spaced with respect to the sleeve 32. Thus, when the exhaust impulses strike the sheet it will be flexed and any ice which may form on the sheet will be broken up and be carried to the atmosphere by the stream of exhaust fluid.

In practice, the present invention has been 1 found to be a highly efiicient device for suppressing the sound vibrations caused by the intermittent impulses of the exhaust fluid flowing from the piston chamber. During its passage through the sleeve the exhaust fluid passes in opposite directions from the exhaust port 28, thence in zigzag fashion along different paths to the atmosphere. The exhaust impulses are thereby evened out without causing an appreciable back pressure and the fluid passes through the outlet openings 48 to the atmosphere as a substantially constant stream.

I claim:

1. In a mufliing device, the combination of a pneumatic tool casing having a piston chamber and an exhaust port for the piston chamber, a sleeve to surround the casing and cooperating therewith to define an expansion chamber for exhaust fluid, an outlet opening in the sleeve, and means to prevent contact of the exhaust fluid in the expansion chamber with the casing.

2. In a mufiiing device, the combination of a pneumatic tool casing having a piston chamber and an exhaust port for the piston chamber, a sleeve to surround the casing and cooperating therewith to define an expansion chamber for exhaust fluid, an outlet opening in the sleeve, and a jacket of insulating material encasing the easing to prevent contact of the exhaust fluid in the expansion chamber with the casing.

3. In a muii'ling device, the combination of a penumatic tool casing having a piston chamber and an exhaust port for the piston chamber, a sleeve to surround the casing and cooperating therewith to define an expansion chamber for; the exhaust fluid issuing from the piston chamber, a jacket consisting of insulating material encasing the casing to prevent contact of the exhaust fluid in the expansion chamber with the surface of the casing, and bailles in the sleeve to form a tortuous path for fluid between the exhaust port and the outlet opening and to support the jacket.

4. In a mufiling device, the combination of a pneumatic tool casing having a piston chamber and an exhaust port for the piston chamber, a sleeve to surround the casing and cooperating therewith to define an expansion chamber for the exhaust fluid issuing from the piston chamber, an outlet opening in the sleeve, a jacket of material of low heat conductivity to insulate the casing, and baffles in the sleeve arranged in staggered relationship between the exhaust port and the outlet opening and engaging the jacket to hold said jacket against the casing.

GEORGE H. FUEHRER. 

